High Frequency Satellite Surveillance of Gulf of Mexico Loop Current Frontal Eddy Cyclones

Nan Walker, Robert Leben, Steve Anderson, Alaric Haag, Chet Pilley

As the oil and gas industry migrates towards deepwater exploration, the need to characterize the deep-water environments of the Gulf of Mexico has become increasingly important. This study focused on developing remote sensing tools to study Loop Current Frontal Eddies (LCFEs), which are cyclonic features found along the periphery of the Loop Current (LC). These features have proven problematic for study as they often move rapidly and they do not always have a distinct thermal signature. They play an integral but not completely understood role in separation of warm core rings from the LC and have been discussed as potential trigger mechanisms for high-energy events within the water column and near the bottom along the Sigsbee Escarpment. They are biological oases along the margin of the oligotrophic LC waters. The over-arching goal of this project was to develop and apply new remote sensing methodologies to improve upon the surveillance of ocean features and the understanding of circulation processes in the Gulf of Mexico (GoM). The more specific project goal was to apply these new techniques to improve understanding of the basic characteristics of LCFE cyclones, specifically where they develop, how they evolve as they travel around the LC, frequency of occurrence, and their impacts on surface and deeper ciculation areas of oil and gas operations. Satellite data included GOES sea surface temperatures (SST), sea surface height (SSH) data from several operational sensors, and satellite-tracked drifters.

The new techniques provided metrics on LCFE motion, size, frequency and intensity. Extensive use was made of Hovmoller time/distance graphs comprised of daily "de-clouded" SST composite data (from GOES-8 and GOES-12) for tracking the LCFEs around the entire perimeter of the LC. The 17-cm SSH contour was used as a useful benchmark for the location of the LC on a daily basis. The along track SSH data was essential for determining intensity and size of LCFEs as they evolved along the LC margin. Case study analyses of selected events provided important additional information on LCFE variability during extreme events and their affects on circulation through the water column. These new techniques can be used in real-time to improve on surveillance and modelling capabilities of mesoscale circulation in the GoM.